The present invention relates to apparatus for transporting and classifying discrete articles, especially articles which constitute or form part of smokers' products. More particularly, the invention relates to improvements in article transporting and classifying apparatus of the type wherein at least one conveyor, especially a continuously driven conveyor, has an endless article-supporting component with suction ports serving to attract articles to the supporting component.
In the processing of tobacco, it is often necessary to transport a layer of discrete articles along a path which is defined by two or more conveyors so that the articles must be transferred from conveyor to conveyor, for example, during travel from a making or producing machine to a consuming or processing machine or from a first processing machine to a second processing machine. Articles of the just outlined character include plain or filter cigarettes, cigars or cigarillos, filter rod sections, labels, uniting bands, groups of rod-shaped articles including filter rod sections and plain cigarettes, cigarillos or cigars, pairs of coaxial plain cigarettes or filter cigarettes, or the like. For the sake of simplicity, the following part of the description under this subtitle will discuss the transport of cigarettes with the understanding, however, that other discrete articles of the tobacco processing industry can be treated in the same or in a similar way.
It is well known that plain or filter cigarettes are transported by endless conveyors, especially in the form of rotary drums, during manufacture or processing in cigarette making or filter tipping machines. As a rule, the cigarettes are attracted to the peripheries of such drums by suction which is applied via ports provided in the peripheral surfaces of the drums to ensure retention of the cigarettes in flutes, cradles or directly on the convex peripheral surface of the respective drum. In many instances, the cigarettes are transported in the form of a single layer and their longitudinal axes extend at right angles to the direction of transport (i.e., the cigarettes are transported sideways). The suction ports are connected with a suitable suction generating device during travel along that portion of their endless path wherein the cigarettes should adhere to and share the movement of the respective conveyor. If the cigarettes of the single layer are to be transferred onto the periphery of a next-following drum-shaped conveyor, the application of suction to successive ports is terminated at the station where the transfer from the oreceding conveyor onto the next-following conveyor is to take place, and the suction ports of the next-following conveyor begin to communicate with a suction generating device as soon as they reach the transfer station. In other words, a port which approaches the transfer station and attracts a cigarette to the preceding conveyor is connected with the respective suction generating device whereas a port which approaches the transfer station but is machined into the peripheral surface of the nextfollowing conveyor is disconnected from the respective suction generating device or, even if connected to the respective suction generating device, is not capable of actually attracting a cigarette until it reaches the transfer station.
In most cigarette making, filter tipping or like machines, the means for regulating the flow of air from the suction ports to the respective suction generating device or devices includes so-called valve plates which are grooved discs or plates interposed in the path of air flow from the ports of the conveyors to the suction generating devices and serving to determine the length of those portions of peripheral surfaces of the respective conveyors along which the cigarettes travel on their way to the transfer station. A valve plate can be placed adjacent to one end face of a rotary drum-shaped conveyor, or it can be mounted in the interior of a hollow rotary drum-shaped conveyor to determine the number and orientation of those suction ports which are free to communicate with the suction generating device, e.g., with the suction intake of a blower. The just discussed mode of regulating the number and orientation of those suction ports which are to communicate with the suction generating device is quite satisfactory and does not present serious problems. even in modern high-speed cigarette making, filter tipping or like machines, when all cigarettes of a single layer of such articles are to be transferred from a preceding conveyor onto the next-following conveyor or into storage. Successive suction ports of the preceding conveyor are simply sealed from the suction generating device not later than on arrival at the transfer station so that successive cigarettes of the single layer cease to be attracted to the preceding conveyor and can leave such conveyor under the action of gravity, in response to the stripping action of arcuate or other suitable mechanical separating devices, or in response to attraction by the next-following conveyor whose suction ports begin to communicate with the respective suction generating device not later than when they reach the transfer station.
However, the situation is quite different if certain (selected) cigarettes of the single layer which is transported by the preceding conveyor are to remain on the preceding conveyor while the remaining cigarettes leave the preceding conveyor at the aforediscussed transfer station to be accepted and transported by the next-following conveyor. Such situation can arise, for example, when a layer of cigarettes is transported past a testing device which detects defective cigarettes and generates signals serving to effect segregation of defective cigarettes from satisfactory cigarettes. The segregation can involve retention of satisfactory or defective cigarettes on the preceding conveyor and the transfer of defective or satisfactory cigarettes onto the next-following conveyor. Since the layer contains defective cigarettes in random distribution with satisfactory cigarettes, it is necessary to rapidly change the circumstances prevailing at the transfer station, for example, in such a way that an oncoming defective cigarette will continue to travel with the preceding conveyor past the transfer station but each and every satisfactory cigarette will be transferred onto the next-following conveyor. Such change of circumstances is effected by signals which are generated by the testing device and are transported or advanced in synchronism with (i.e., in imitation of) travel of the respective defective cigarettes to the transfer station. This creates numerous problems in a modern high-speed cigarette making or processing machine which turns out extremely large quantities of cigarettes per unit of time (normally not less than one hundred per second). For example, if the layer which is transported by the preceding conveyor contains a satisfactory cigarette between two defective cigarettes, the suction port or ports which attract the first defective cigarette must continue to communicate with the respective suction generating device during transport past the transfer station, the next suction port or ports which attract the satisfactory cigarette must be disconnected from the suction generating device on arrival at the transfer station so that the satisfactory cigarette can be taken over by the next-following conveyor, and the next suction port or ports must again continue to communicate with the suction generating device in order to ensure that the second defective cigarette will advance past the transfer station and remain on the preceding conveyor. In other words, it is often necessary to shift from retention to release or vice versa within extremely short intervals of time such as are required to transport a suction port through a distance corresponding to that between two neighboring cigarettes of the layer on the first conveyor. The duration of each such interval is in the range of a few milliseconds. Heretofore known devices which are used to connect the oncoming suction ports with or to disconnect the oncoming suction ports from the suction generating device are not sufficiently reliable to guarantee selective retention of cigarettes on the preceding conveyor when the cigarettes are transported at speeds which are required in a modern cigarette maker, filter tipping machine or the like.